A molten carbonate fuel cell (MCFC), which obtains electric power by an electrochemical reaction between hydrogen and oxygen, is constituted by interposing an electrolyte (carbonate) between a fuel electrode (anode), for example, formed from a nickel porous material and an air electrode (cathode), for example, formed from a nickel oxide porous material. In the MCFC, hydrogen (H2) obtained from a fuel, such as a natural gas, is supplied to the anode, while air (O2) and carbon dioxide (CO2) are supplied to the cathode, whereupon power generation is performed by an electrochemical reaction between H2 and O2. The MCFC is characterized, for example, by having a high efficiency because of its operation at high temperatures, and by minimally affecting the environment because of its ability to recover and separate CO2. In recent years, therefore, the MCFC has been drawing attention as a power generation system following water power, thermal power, and nuclear power.
Since the MCFC operates at high temperatures, moreover, the MCFC may be configured to supply its exhaust to a combustor of a gas turbine. Based on this configuration, a power generating plant combining MCFC and a gas turbine (i.e., combined power generation equipment) has hitherto been proposed (see, for example, Patent Document 1) The combined power generation equipment comprising the MCFC gas turbine combination enables the MCFC and the gas turbine to perform power generation.
With the MCFC which obtains electric power by an electrochemical reaction between hydrogen and oxygen, it is conceivable to obtain a hydrogen gas by reforming a fuel gas, such as a natural gas, in order to acquire hydrogen as a fuel. On the other hand, various technologies have been proposed for gasifying coal, which is supplied highly stably and whose price per unit calorific value is low, to use the resulting gas as a fuel for a fuel cell (see, for example, Patent Document 2).
However, the fuel cell using the gas from coal as the fuel is mainly a solid oxide fuel cell (SOFC) operating at high temperatures. In the field of MCFC capable of operation with high efficiency, no technologies for gasifying coal and using the resulting gas as a fuel have been established. Nowadays, coal has a larger amount of CO2 emission per unit calorific value than does a natural gas, so that a plant giving consideration to the reduction of CO2 needs to be constructed. Actually, there has been a demand for the realization of a plant using a fuel produced by gasification of coal (may hereinafter be referred to as a coal gasification fuel), while maintaining the performance of MCFC and taking the reduction of CO2 into consideration.
The same can be said of the use of a gas obtained by gasification of not only coal, but also a source other than a natural gas, including, for example, a gas upon gasification (may hereinafter be referred to as a gasification gas) which has resulted from the combustion of a solid fuel such as biomass; or a gasification gas resulting from the combustion of a liquid fuel such as gasoline or light oil; namely, a gas substantially containing a CO gas. Even with the use of such a CO gas-containing gas, there has been a demand for the realization of a plant which takes the reduction of CO2 into consideration while maintaining the performance of MCFC.
Patent Document 1: JP-A-11-135139
Patent Document 2: JP-A-2000-48844